For one thing, 15 Central Park West, on the corner of West 61st Street and Central Park West, is set in a much more established residential neighborhood. It was always marketed as as "family building" and for "New Yorkers who lived here already," Gross said.

One57, on the other hand, is a few blocks to the south and east in a neighborhood that's not exactly known for its residential life. Buyers in this new glass building have admitted they plan to use it as a trophy home or crash pad when they are in Manhattan for business.

Foreign buyers have been dominating the New York luxury real estate market in the past couple years, and this is especially true in 15 Central Park West's re-sale market and for the first-time buyers at One57.

That's the main difference between 15 Central Park West and One57 right now: the type of first time buyers, according to Gross.

Gross acknowledged that it's hard to tell for sure what a new luxury building's story will be when it's still under construction, but it's hard not to pay attention to a building with so much hype.

"It's clear (Gary Barnett of Extell Development) is trying to take a past model and make it applicable to a new century," Gross said. "And to me that the fact that it is both modern and part of the continuum of luxury development in New York, That's what makes it fascinating."